How do you factor #ab - 5a + 4b - 20?

May 14, 2015

$a b - 5 a + 4 b - 20$

Group

$\textcolor{red}{\left(a b - 5 a\right)} + \textcolor{b l u e}{\left(4 b - 20\right)}$

Extract factor from each group

$\textcolor{red}{\left(a\right) \left(b - 5\right)} + \textcolor{b l u e}{\left(4\right) \left(b - 5\right)}$

Extract the $\left(b - 5\right)$ factor from each term

$\left(\textcolor{red}{a} + \textcolor{b l u e}{4}\right) \left(b - 5\right)$